As a method for manufacturing the color filter, a photolithography has been widely used for a long time. The photolithography is a method including: coating and drying a coloring photosensitive composition on a support to form a colored layer, then exposing and developing the colored layer to form a colored pixel of a first tint (for example, green), and forming a colored pixel of the remaining colors in the same manner.
However, as the pixels of a solid-state imaging device are micronized, it has become difficult to achieve both spectral characteristics and pattern formability of a color filter for the demand for micronization and thinning of the color filter in the pattern formation by a so-called photolithography. Specifically, in a color filter for a solid-state imaging device, the thickness thereof tends to become, for example, 1 μm or less for the thinning of a colored pattern and to become 2 μm or less (for example, 0.5 μm to 2.0 μm) for the pixel pattern size, thereby achieving a microsize.
In particular, as the thinning of a film progresses, the relative amount of colorants such as pigments in a film increases, while the amount of components other than the colorants, which contribute to the photolithographic properties, in a film relatively decreases, and the pattern formability due to the decrease has effects of improving the shape of a pattern observed on the top surface thereof even when a correction such as OPC is performed for the requirement of forming a pattern below 2.0 μm, but there is a problem such as insufficient rectangularity that the pattern edge of the pattern shape is round when observed the cross-section. It is known that in a color filter (a color filter manufactured by photolithography using a coloring radiation sensitive composition in which a pigment is dispersed in various compositions) using a pigment dispersion liquid, the rounding of the pattern edge become significant by influence of light scattering by the pigment when exposing.
In particular, recently, due to the demand for the higher definition of the color filter for a solid-state imaging device, the formability of a pattern of, for example, 1.4 μm becomes problematic, and thus, the resolution may almost reach a limit in the photolithography in the related art.
For a method for manufacturing a color filter using the photolithography, a processing method using dry etching has been suggested as a method effective to realize micronization and thinning of a pattern. The dry etching has been adopted in the related art as a method for forming a pattern (each colored pixel) in a rectangular form, and a method for forming a pattern which combines the photolithography and the dry etching have been suggested (see, for example, Patent Documents Japanese Patent Application Laid-Open No. 2006-222290 and Japanese Patent Application Laid-Open No. 2007-48774).
In order to manufacture a color filter of a plurality of colors for use of a solid-state imaging device such as an image sensor, a colored layer of a second tint is stacked, for example, so as to cover a colored pattern of a first tint, which is processed into a desired pattern. Thereafter, the colored layer of the second tint is planarized by a planarization treatment until at least the colored layer of the first tint is exposed, thereby forming a colored pattern of a second tint. Further, a colored layer of a third tint is stacked so as to cover the colored patterns of the first tint and the second tint, and the colored layer of the third tint is removed, and simultaneously a colored pattern of the third tint is formed by exposing and developing using a photolithographic technology. At this time, there has been a problem in that, if residue caused by the colored layer of the third tint (specifically, residue generated during development of the colored layer of the third tint) is present on a layer planarized by the planarization treatment, the spectra of the first colored layer and the like are changed, resulting in a reduction of a device sensitivity. It is thought that, if the colored layers having different colors are removed from the layer planarized by the planarization treatment by exposure and development, components of the colored layer are easily adsorbed on the layer planarized by the planarization treatment, and thus, residue is easily generated.
The present invention has been made in consideration of the above-described problems, and an object of the present invention is to provide a method for manufacturing a color filter by stacking a plurality of colored layers, in which the generation of residue may be suppressed by a planarization treatment, a color filter and a solid-state imaging device.